Hydraulic system

ABSTRACT

A hydraulic system employing a pressure compensated variable displacement pump in which the pressure and volume control of the pump are interconnected for simultaneous adjustment within a range in a predetermined relationship.

United States Patent 1 1 1111 3,740,167 Albrecht June 19, 1973 HYDRAULICSYSTEM 2,835,228 5/1958 Park et a1. 417/222 3,588,286 6 1971 Skinner91/506 [75] Inventor. Davld Eugene Albrecht, Blue Bell, 1,748,606 2,1930lngoldbym 417/222 3,163,115 12/1964 Nerf et al 417 222 Assignees: DavidE. Albrecht, Blue 3,250,227 KOUl'lS 417/222 Ra mond H Jensen Plymouth3,302,585 2/l967 Adams et al 417/222 Meyeting 3,489,094 1/1970 Vaughanet a1] 417/222 22 H J 19;) FOREIGN PATENTS 0R APPLICATIONS I 1 2,017,6564 1970 Germany 417 222 Appl. No.: 49,134

52 US. Cl. 417/218 51 Int. Cl. F0lb49/00 [58] Field of Search 417 213,218,222;

[56] 1 References Cited 7 UNITED sTATEs PATENTS 2,283,321 5/1942 D08 etal. 60/52 us 2,298,358 10/1942 Ernst 60/52 us Primary Examiner-WilliamL. Freeh Attorney-Busser, Smith & Harding 57 ABSTRACT A hydraulic systememploying a pressure compensated variable displacement pump in which thepressure and volume control of the pump are interconnected forsimultaneous adjustment within a :range in a predetermined relationship.

5 Claims, 4 Drawing Figures Patented June 19, 1973 3,740,167

2 Sheets-Sheet l CONTROL 2O wonx LOAD FIG. I.

mxmuu mxmuu FLOW HORSEPOWER PRESSURE SETTING SETTING (6,204.) (PSI)CONSTANT HORSEPOWER INVENTOR DAVID EUGENE ALBRECHT FIG.4. BY

ATTORNEYS Patented June 19, 1973 3,740,167

2 Sheets-Sheet 2 m I \g g a) s!\ l -j-1 r-i I}: o o Lit: N 3 WE 2 M:

I I 23 A T W f E l INVENTOR 4; DAVID EUGENE ALBRECHT ATTORNEYS HYDRAULICSYSTEM BACKGROUND OF THE INVENTION This invention relates to hydraulicsystems and particularly to a hydraulic system employing a pressurecompensated variable displacement pump to deliver a volume of fluidunder pressure to a work load.

In a hydraulic system the work done per unit time (horsepower) isdirectly proportional to the volume delivered and the delivery pressure.Most hydraulic systems employ a hydraulic cylinder or fluid motor toperform the work on a machine. A cylinder imparts linear motion whereasa fluid motor imparts rotary motion.

With respect to a cylinder, it will be apparent that the higher thehydraulic pressure, the greater is the force capability of the cylinder,and the higher the flow to the cylinder, the higher will be the speed atwhich the cylinder will operate. Likewise, with respect to a fluidmotor, the higher the hydraulic pressure the greater will be the torquecapability of the motor, and the higher the flow volume to the motor,the higher the speed at which the motor will rotate.

Typically, a hydraulic pumping system of the prior art is set for themaximum volume and the maximum pressure for which the system isdesigned. However, these two factors in the maximum condition may not berequired simultaneously. It is desirable in such a system, to be able tovary infinitely the flow volume delivered and the delivery pressure inrelation to one another in such a manner as would permit the system todeliver the optimum system requirement throughout the flow and pressureranges. An example of such a de-' sired application is a spindle drivethat requires a constant horsepower output. In a typical hydraulicsystemof the prior art wherein the flow volume and pressure are set atmaximum system limits, the horsepower available at the spindle isdirectly proportional to the spindle speed. This results in less thanoptimum utilization of the horsepower input.

SUMMARY OF THE INVENTION It is the general object of the invention toprovide a hydraulic pumping system which is controlled so that thedesirable flow/pressure condition can be obtained by employing apressure compensated variable displacement pump which is controlled toproduce this re sult.

Briefly stated, the control system in accordance with the invention isemployed in a hydraulic system for delivering fluid to a work load andcomprises a pressure compensated variable displacement pump adapted tohave the maximum delivery volume and its maximum delivery pressurevaried infinitely within a range. This pump also has means for settingthe pressure and the volume to any desired setting within the pressureand volume ranges. The essence of the invention is the provision of acontrol means which interconnects said volume setting means and saidpressure setting means for simultaneously varying said pressure andvolume settings in a predetermined relationship.

In the pumps of the indicated type the operation is such that the pumpwill always deliver its maximum set flow rate unless the system pressuregets as highas the maximum pressure setting on the pump, in which casethe pump will only deliver enough flow to maintain this system pressure.Also with this type of pump, means are provided for setting the pumpsdisplacement from zero (no flow) to maximum pump delivery. The pump isalso adapted to permit the maximum pressure setting to be adjustedinfinitely within the pressure limits of the pump. In accordance withthe invention there is provided a control system which interconnects thevolume adjustment and the pressure adjustment of the pump in a mannersuch that said volume setting means and said pressure setting means canbe simultaneously varied in A more specific application of the controlsystem in accordance with the invention is the provision of a constanthorsepower drive system where the control can be set to give a constanthorsepower over a range of operation in which as the flow settingdecreases, the pressure setting may be simultaneously increased.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic showing of thehydraulic system employing the control means in accordance with theinvention;

' FIG. 2 is a detailed showing of the control means employed in thehydraulic system in accordance with the invention;

FIG. 3 is a diagrammatic illustration of the control means as viewed onlines 33 of FIG. 2; and

FIG. 4 is a graph illustrating an application of the hydraulic system inaccordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring initially to FIG. 1his noted that this Figure '7 shows a typical circuit schematic for thehydraulic system employing the invention. This system includes aconventional pressure compensated variable displacement pump 10 whichreceives the hydraulic fluid from a reservoir 12 by means of a line 14and delivers the same to a suitable work load 16 by way of line 18, thereturn line from the work load being indicated at20. The pressurecontrol for the pump 10 is indicated at 22 and the volume control forthepump 10 is indicated at 24. The pressure control 22 and the volumecontrol 24 are operated by the novel control means in accordance withthe invention indicated generally at 26. Variable displacement pumps ofthe indicated type are conventional, one such pump being made by theDelavan Manufacturing Co. of West Des Moines, Ia. and being disclosed inthis companys Manual No. 1211A wherein such a pump is designated asModel No. PV320 and described as a pressure compensator variabledisplacement pump. This pump is a positivedisplacement axial pistonpump. in which a cylinder is rotated so pistons are driven back andforth in their cylinders in the direction parallel to the pump shaft.The basic construction of such a pump is disclosed in U.S. Pat. Nos. Re.26,519, 3,221,660, and 3,350,881.

1n the operation of this type of pump, a cylinder rotor with its pistonsis rotated on a shaft so that the pistons are driven back and forth intheir cylinders in a direction parallel to the shaft, liquid beingforced into the cylinders by pressure differences while the pistons aremoving outwardly and liquid being forced out of the pistons while thepistons are moving inwardly. The pump is provided with means whereby thedistance the pistons will move back and forth is set by the tilting of acam reaction plate so that the angle of the cam reaction platedetermines the piston stroke and accordingly the pump displacement.

The pump is provided with a volume limit adjustment whereby the maximumvolume desired to be pumped can be set, such means comprising anadjustment screw which limits the maximum angle of the cam reactionplate. The pump is also provided with an adjustment means which sets thedesired pressure of the pump, such means comprising an adjustment screwwhich operates on a pressure compensating spring of a pressure controlvalve which controls a pair of pistons which control the position of thecam reaction plate to limit the discharge pressure of the valve to theset amount.

It is to be noted that the hydraulic system in accordance with theinvention may utilize various of the pressure compensated variabledisplacement pumps known in the art and is not limited to the particulartype described above. Since these pumps are conventional and well knownin the art, further description thereof is not deemed necessary.

Referring to FIG. 2 there is shown the pump which comprises the pressurecontrol 22, which includes an adjustment screw indicated at 32, and thevolume limit control 24, which includes an adjustment screw indicated at34. As viewed from the right in FIG. 2, the pressure adjustment screw 32is turned in a clockwise direction to increase the pressure and in acounter-clockwise direction to decrease the pressure whereas the volumeadjustment screw 34 is turned in a clockwise direction to decrease thevolume and in a counter-clockwise direction to increase the volume.

The control means 26 comprises a sprocket 40 mounted on a shaft 41drivingly connected to pressure adjustment screw 32 by way of a coupling42 and a sprocket 44 mounted on a shaft 45 drivingly connected to theadjustment screw 34 by way of a coupling 46. There is also provided acontrol shaft 50 which carries a control knob 52 on one end thereof.Shaft 45 is journalled in a bearing support 47 mounted on the pump or asupporting frame. Mounted on the control shaft 50 is a sprocket 54 whichcarries a drive chain 56 which is connected to the sprocket 40 on thepressure adjustment shaft 41. There is also provided another sprocket 58on the control shaft 50 which is interconnected with the sprocket 44 onthe volume adjustment shaft 45 by means ofa chain 59 as shown in thedrawing. By means of this arrangement the pressure adjustment and thevolume adjustment of the pump 10 are are interconnected by means of thecontrol means 26 so that they may be simultaneously adjusted. Moreover,it will be apparent that this adjustment is designed so that thepressure adjustment and the volume adjustment may be varied in apredetermined relationship which depends upon the size and arrangementof the various interconnecting parts (i.e. sprockets and chains).

From a consideration of FIGS. 2 and 3, it will be noted that therotation of the control knob 52 in a clockwise direction will cause acorresponding clockwise rotation of shafts 50, 41 and 45, and by reasonof the connection through couplings 42 and 46, there will also beimparted a clockwise rotation to the pressure adjusting screw 32 and thevolume adjusting screw 34 (the rotation of the control means 26 beingindicated by the arrows in FIG. 3). As was discussed above, theclockwise rotation of the pressure adjusting screw 32 will cause anincrease in the pressure adjustment of the pump and by reason of theclockwise rotation of volume adjustment screw 34, this will cause adecrease in the volume adjustment of the pump. Moreover, it will beapparent that by reason of the connection by way of the sprockets shownin FIG. 3, the increase in the pressure adjustment will be in apredetermined relation with the decrease in the volume adjustment. Onthe other hand when the control knob 52 is turned in thecounter-clockwise direction, the effect on the pressure and volumesettings will be the reverse, namely there will be a decrease in thepressure adjustment and an increase in the volume adjustment, and,again, these adjustments will be in a predetermined relationship.

It will be apparent that by a simple mechanical rearrangement of theparts, such as a criss-crossing of one of the belts 56 or 59, it ispossible to reverse the abovediscussed control relationships. This issimply a matter of choice in design and is related to the resultsdesired.

Moreover, it will also be apparent that although the disclosedarrangement shows the two controls mechanically innerconnected by achain and sprocket means, a similar control action can be achieved withvarious mechanical connections such as gears, a rack and pin ionarrangement, etc., and may also be achieved by other means, such aselectrical, pneumatic or hydraulic means, etc.

One important specific application of the hydraulic control system inaccordance with the invention is the provision of a constant horsepowerdrive system where the control would be set to produce a constanthorsepower over a range of operation. This would be achieved by settingthe volume control so that as its setting is progressively decreasedlinearly, the pressure is progressively increased linearly so as tomaintain a constant horsepower relationship throughout the range ofoperation. This arrangement is illustrated graphically in FIG. 4. It isnoted that the control arrangement shown in FIG. 3 is specificallydesigned to achieve a constant horsepower output for a pump of theindicated type. However, it would be obvious that the characteristics ofthe pump and the adjustment means provided thereon will require theadaption of the control means in order to achieve the linearrelationship which will produce the constant horsepower output discussedabove.

It will also be apparent that by determining the particular relationshipbetween the volume and pressure settings, it is possible to achievevarious relationships to produce various horsepower conditions inaddition to the constant horsepower condition discussed above.

It will be evident that changes may be made in the construction andarrangement of parts without departing from the scope of the invention.Accordingly, it is not desired to be limited except as set forth by thefollowing claims.

I claim:

1. In a hydraulic system for delivering fluid to a work load, a pressurecompensated variable displacement pump adapted to have the maximumdelivery volume thereof set within an infinitely variable flow range andthe maximum delivery pressure thereof set within an infinitely variablepressure range, means for setting the maximum delivery volume of saidpump to a desired setting within said flow range, means for setting themaximum delivery pressure of said pump to a desired setting within saidpressure range, said pump being constructed and arranged to deliver themaximum set volume of flow until the system pressure reaches the maximumset pressure whereupon the pump will only deliver enough flow tomaintain the system pressure, and control means for simultaneouslyvarying said pressure and volume settings in a predeterminedrelationship, said control means including means interconnecting saidvolume setting means and said pressure setting means for adjusting onesetting to a predetermined desired setting as the other setting isadjusted to a corresponding predetermined desired setting.

2. In a hydraulic system according to claim 1 wherein said control meansis arranged to simultaneously adjust said pressure setting means andsaid volume setting means to increase the pressure setting andidecreasethe volume setting and vice versa.

3. In a hydraulic system according to claim 1 wherein said volumesetting means includes an adjustable screw, said pressure setting meansincludes an adjustable screw, and said control means includes anadjustable member and means interconnecting said adjust able member witheach of said adjusting screws.

4. In a hydraulic system according to claim 3 wherein said control meansis arranged to simultaneously adjust said pressure setting means andsaid volume setting means to increase the pressure setting and decreasethe volume setting and vice versa.

5. A hydraulic system according to claim 2 wherein said control means isconstructed and arranged so that said pressure setting is varied in alinear relationship relative to said volume setting.

1. In a hydraulic system for delivering fluid to a work load, a pressurecompensated variable displacement pump adapted to have the maximumdelivery volume thereof set within an infinitely variable flow range andthe maximum delivery pressure thereof set within an infinitely variablepressure range, means for setting the maximum delivery volume of saidpump to a desired setting within said flow range, means for setting themaximum delivery pressure of said pump to a desired setting within saidpressure range, said pump being constructed and arranged to deliver themaximum set volume of flow until the system pressure reaches the maximumset pressure whereupon the pump will only deliver enough flow tomaintain the system pressure, and control means for simultaneouslyvarying said pressure and volume settings in a predeterminedrelationship, said control means including means interconnecting saidvolume setting means and said pressure setting means for adjusting onesetting to a predetermined desired setting as the other setting isadjusted to a corresponding predetermined desired setting.
 2. In ahydraulic system according to claim 1 wherein said control means isarranged to simultaneously adjust said pressure setting means and saidvolume setting means to increase the pressure setting and decrease thevolume setting and vice versa.
 3. In a hydraulic system according toclaim 1 wherein said volume setting means includes an adjustable screw,said pressure setting means includes an adjustable screw, and saidcontrol means includes an adjustable member and means interconnectingsaid adjustable member with each of Said adjusting screws.
 4. In ahydraulic system according to claim 3 wherein said control means isarranged to simultaneously adjust said pressure setting means and saidvolume setting means to increase the pressure setting and decrease thevolume setting and vice versa.
 5. A hydraulic system according to claim2 wherein said control means is constructed and arranged so that saidpressure setting is varied in a linear relationship relative to saidvolume setting.